Due to their composition, cosmetic agents can serve as a nutrient for germs and microorganisms. These germs can on the one hand cause microbial contamination of the consumer, and on the other hand they can alter the ingredients of the cosmetics and thereby form substances which have undesired effects such as sensitization or skin irritation. To prevent these undesired consequences and to ensure a particular shelf life of the cosmetics, said cosmetics must be preserved. Since preservatives in turn have the potential to cause irritation, the use thereof in cosmetics is strictly regulated.
Cosmetic products for changing the color of hair usually include substantive dyes and/or oxidation dye precursors. When using substantive dyes, the dye which already exists in finished form is applied to the keratin fibers.
Oxidation dye precursors are included in oxidative coloring agents. These involve so-called developer components and coupler components which together form the actual dyes only under the effect of oxidizing agents (usually hydrogen peroxide). Oxidative coloring agents are characterized by long-lasting color results.
Oxidative coloring agents are usually applied in an alkaline medium and require the presence of hydrogen peroxide. Since hydrogen peroxide itself has biocidal and preserving properties, it is usually not necessary to add further preservatives besides the hydrogen peroxide to oxidative color change agents. Under certain conditions, however, it may still be necessary to preserve oxidative coloring agents.
Oxidative coloring stresses the hair and is therefore usually repeated only after a period of 6 to 8 weeks. Over this time, however, the hair grows and the non-colored hair at the roots becomes visible. This difference in color between colored and non-colored hair is often perceived as highly unattractive by the consumer. One possibility for hiding these color differences is to color the roots. Coloring of the roots is carried out specifically only at the roots, for example 2 to 3 weeks after the regular coloring carried out on the full head of hair. Since this coloring of the roots takes place as an additional intermediate coloring between the regular coloring procedures carried out on the full head of hair, it creates an additional stress on the hair and should therefore be as gentle as possible. Root coloring agents therefore either include only substantive dyes, or else hydrogen peroxide is used in very low concentrations. The reduction of the concentration of hydrogen peroxide or the complete omission of the latter may make it necessary to use additional preservatives.
In addition, root coloring products are often presented in such a way that the quantity thereof is sufficient for treating the roots multiple times. The bottle or tube containing the color cream is repeatedly opened and closed by the user in order to withdraw the portion required for the individual root treatment, and therefore there is a risk of contamination of the product by germs or microorganisms. For this reason, too, a preserving of these coloring agents is necessary.
It is therefore desirable to discover effective preservative mixtures with good suitability for hair coloring agents. The intention for the preservatives is for such to be suitable for hair coloring agents for coloring the roots of the hair which are repeatedly opened and emptied in portions. The aim for the preservatives should be to prevent any colonization of the coloring agent or of the skin and scalp with undesired germs, while having no adverse effect or no significant adverse effect on the natural skin flora.
It is also desirable when using the preservatives in the coloring agent for the keratin fibers to be colored in bright intensive colors. In particular, it is desirable for no color shifts to occur as a result of using the preservatives, and for reactions between dyes and preservatives to be avoided, along with the formation of undesired by-products. In addition, it is desirable for the color-fastness properties not to be adversely affected by the use of the preservatives.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with this background of the invention.